1. Field of the Invention
The present invention relates to an X-ray monochromator, a method of manufacturing the same and an X-ray spectrometer using such an X-ray monochromator.
2. Description of the Related Art
An X-ray monochromator is employed in an X-ray spectrometer having a configuration as illustrated in FIG. 6 of the accompanying drawings. Referring to FIG. 6, an X-ray monochromator 110, an X-ray source 12 and an X-ray detector 13 are arranged on a Rowland circle 14 having a radius R with its center located at point A. The X-ray source 12 is, for example, a sample that generates fluorescent X-rays. X-rays (incident X-rays 16) that are irradiated from the X-ray source 12 and that include a variety of wavelength components are reflected at different positions of the X-ray monochromator 110 and reflected X-rays 17 are focused at the detection surface of the X-ray detector 13, where the intensity of focused X-rays is observed. A phenomenon of diffraction is utilized for the reflection of X-rays and only X-rays of specific wavelengths that satisfy the Bragg condition (formula 1) shown below are observed by the X-ray detector 13. The intensity of X-rays of each wavelength that corresponds to the formula 1 can be measured by moving the X-ray source 12 and the X-ray detector 13 on the Rowland circle 14 and shifting the incident angle θ at reflection point C.2d sin θ=nλ  (Formula 1)
(where d: structural period, θ: incident angle, angle of diffraction (Bragg angle), n: degree of diffraction, λ: X-ray wavelength).
The X-ray monochromator 110 has a structural periodicity directed to point B at each reflection position thereof so as to satisfy the requirement of the formula 1, the structural period being d in the formula 1. Namely, the X-ray monochromator 110 is formed by using a member that is curved with a radius of curvature equal to the diameter (2R) of the Rowland circle 14 and made of a material that shows a periodicity in the normal directions of the curved surface.
Additionally, the X-ray monochromator 110 preferably has a surface profile stretching along the Rowland circle 14 so that reflected X-rays 17 are focused at the position of the X-ray detector 13. A monochromator arranged in such a way is referred to as Johansson monochromator. However, Johann monochromators having a surface profile stretching along a circle 15 with a radius equal to the diameter (2R) of the Rowland circle as illustrated in FIG. 6 are often employed.
When the wavelengths of X-rays are relatively long, artificial multilayer film mainly made of an inorganic material and having a structural period of several nanometers is often selected as structurally periodic material to be used for an X-ray monochromator from the viewpoint of easiness of modifying the structural period. A material having a low electron density such as an organic material for artificial multilayer film in order to improve the spectroscopic performance of X-rays can be used. Japanese Patent Application Laid-Open No. S63-94200 discloses an X-ray monochromator using clay having a layered structure and including organic cations in layered spaces and mica minerals as structurally periodic material.
On the other hand, Japanese Patent Application Laid-Open No. 2005-246369 (which corresponds to U.S. Pat. No. 7,618,703) discloses a porous film having a periodic structure formed via self-assembly of molecules and an application thereof to X-ray optical elements. The disclosed porous film shows a symmetric reflection plane that is directed in a same direction over the entire film and has an axis of rotation (n=6). X-ray diffractions in in-plane directions of such a porous film attributable to the symmetry of the film are applied to X-ray devices. A splitter for which X-rays are made to enter such a porous film on the condition of total reflection so that the splitter separates totally reflected X-rays from X-rays diffracted in-plane and a modulator utilizing that the in-plane intensity of diffracted X-rays changes as a function of the direction of X-rays entering such a porous film have been reported.